1. Field of the Invention
The present invention relates to an operation-delayed switching circuit arranged to be operative after the laspe of a predetermined delay time from its connection to a power source.
2. Brief Description of the Prior Art
As the switching circuit of the aforesaid type, there has been one provided with CR (capacitor-resistor) time constant ciruitry and arranged to be operative so that the delay time is determined by the charge-up characteristics of a capacitor of this CR time constant circuit. This switching circuit has such an advantage that it is simple in construction.
However, with switching circuit of the prior art, electric charge continues to be stored in the capacitor of the CR time constant circuit over a considerably lengthy period of time even after the switching circuit which is in its operative state is disconnected from the power source. Therefore, in case this switching circuit is connected again to the power source before this charge has not been completely discharged, the switching circuit will be brought to its operative state prior to the lapse of the pre-set delay time. Thus, the delay time of the conventional switching circuit can vary depending on the time at which this circuit is connected to the power source.